How do we know where to look for dinosaur fossils?
July 20121:54 min
Dinosaur fossils are found almost exclusively in sedimentary rocks, which form when sand, silt, mud, and organic material settle out of water or air to form layers that are then compacted into rock. Paleontologists look for fossils in sedimentary rocks that were deposited on the continents, primarily by rivers and streams, or in lakes into which the streams emptied. Occasionally, dinosaur fossils are also found in sedimentary rocks representing ancient, desert sand dunes. The sedimentary rocks must have been formed or deposited during the Mesozoic Era, the geologic time period when nonavian dinosaurs lived.